Electrical relay



July 30, 1946. H. J. cARLlN ELECTRICAL RELAY Filed March 18, 1944 UnderWeyl/en@ INVENTOR ATTORN EY Patented July 30, 1946 ELECTRICAL RELAYHerbert J. Carlin, East Orange, N. J., assignmto Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication March 18, 1944, SerialNo. 527,059

12' Claims. 1

This invention relates to an electrical device responsive to the phaserelationship between two alternating quantities and it hasparticularrelation to such an electrical device wherein the aforesaid phaserelationship isdependent on. a variable quantity, such as the frequencyof a source of alternating electrical energy.

The frequency-responsive'devices, such as electrical relays, employed inthe past have utilized two electromagnets associated with a commonarmature structure. Frequency relays of this type are disclosed, forexample, in the Relay Handbook, published in 1926vby the NationalElectric Light Association of New York city. The construction andservicingr of these prior art frequency relays is complicated because ofthe requirement of two electromagnets therefor. Furthermore, such relaysare difficult to compensate for errors introduced by variations in. theapplied voltage and by variations in ambient temperature.

In accordance with the invention, an electrical device, such as afrequency relay, is responsive to the phase relationship between twoalternating quantities. The device includes a directional element whichis directionally responsive to the deviation of the phase relationshipofthe two alterhating quantities from a predetermined value. In aspecific embodiment of the invention, an induction type directionalelement is provided wherein two windings, when energized by currentsdiffering in phase relative to each other, produce a shifting magneticfield in an air gap. An electroconductive armature is positioned in theair gap for rotation in response to the shifting magnetic field and maybel employed for operating an electrical switch or for any other desiredpurpose. 'The windings of the induction type directional element areconnected respectively in two parallel arms of an electrical circuitwhich is energized in accordance with the voltage of a source ofalternating electrical energy. The impedances of the arms includeYreactive components designed to provide a phase relationship betweencurrents flowing in the two arms which vares'as a functionfofthefrequency ofthe voltage applied to 'the electrical circuit. The rangeofvariation is such thatthe currents in the two parallel arms are inphase at a predetermined frequency value. When the frequency passesthrough the aforesaid predetermined value, areversal occurs in thedirection of the torque applied to the armature of the directionalelement. This reversal in .torque may befemployed to actuatea switchassociated witlithe armature.

Byr inserting a suitable adjustable impedance Yin either or both of theparallel arms of the electrical circuit, the value of frequency at whichthe currents in the two arms are in phase readily may be adjusted. Suchadjustments have substantially no effect onthe timing characteristics oftheidevice, and the'time delay of the Ydevice may be adjustedconveniently by adjustment of the distance between the fixed and'movablecontacts of the switch actuated by the armature element. By correctconstruction of the impedances in the two parallel arms, errorsintroduced by variations in applied voltage and in ambient temperaturemay be held to extremely small values.

It is, therefore, an object of the invention to providean improvedelectrical device which is responsive to the phase relationship betweena plurality of alternating quantities.

It is a further object of the invention to provide an electrical deviceresponsive to the phase relationship between a plurality of alternatingquantities wherein such phase relationship is controlled by a singlevariable quantity.

It is any additional object of the invention` to providea. frequencyrelay which is responsive to thephase displacement between currents inparallelarmsof an electrical circuit and wherein the parallel. arms havevalues of impedance which are dependent on the frequency of an appliedalternating quantity for the purpose of 'controlling the v phasedisplacement between the aforesaid currents..

Other objects Aof the invention will be apparent from the followingdescription, taken in conjunction with the accompanying drawing, inwhich:

Figure 1 is aschematic view, with parts in perspective and parts brokenaway, of an electrical system embodying a relay designed in accordancewith the invention;

Figs. 2 and 3 are vector diagrams showing voltage and currentrelationships in the system of Fig. l.; and

Figs. 4.and5 are schematic views with parts in elevation, and with partsbroken away, showing a modification of the relay of Fig. 1.

Referring to the drawing, Figure 1 shows an electrical device which isresponsive to the phase relationship between a` plurality of alternatingcurrents." This device includes a directional element-which isillustrated as of the induction type. A suitable directional element mayinclude a magnetic structure having a pair of pole pieces Sand 5 and athird pole piece 'I'which is spaced fromthe aforesaid-pair to definev anair gap. An eleotroconductive armature 9 is positioned in the air gapand mounted on a shaft l i for rotation in suitable bearings i3 and i5.Conveniently, the armature 3 may be formed of an electroconductivematerial such as copper or aluminum.

Windings if and i9 are positioned on the pole pieces 3 and In addition,a winding 2l is positioned on the pole piece l'. As well understood inthe art, when the windings Il and i3, on the one hand, and the winding 2l on the other hand, are energized by alternating currents which aredisplaced in phase from each other, magnetic fluxes are produceddisplaced in time phase, and thus effectively a shifting magnetic fieldis produced in the air gap between the pole pieces. This shiftingmagnetic eld is effective for rotating i the armature il. The directionof rotation of the armature depends on the direction of phasedisplacement of the current flowing through the windings i? and lil fromthe current flowing through the winding 2i. ture 9 may be damped in aconventional manner by means of a permanent magnet 23 which ispositioned to direct magnetic flux through the armature.

Rotation of the armature may be employed in any desirable manner. Forthe purpose of illustration, the shaft ii carries a contact 25 which ismovable between a stop 2l and a contact 29 in response to rotation ofthe shaft Il. The contact 29 or the stop 2l, or both of these elementsmay be adjustable about the axis of the shaft if. 'Io permit suchadjustment, the contact 29 is mounted on a lever 3i which is rotatableabout the axis of the shaft ll. The arm 3l may be secured in anyposition of adjustment by means of a clamping screw 3B which passesthrough a slot in a cylindrical guide strip 37. Adjustment of the stop'2l may be effected in a similar manner by providing a clamping screw 34therefor. 2l may carry pointers 32 and 32a which overlie a scale 33suitably calibrated to indicate the position or adjustment of thecontact 29 or the stop 2l. In most cases adjustment of the stop 21 alonesuffices for adjusting the relay timing.

Relative mov-ement of the contact 25 and 29 may be employed for anysuitable control function. In the specific embodiment of Fig. 1,engagement of the contact 25 with the contact 29 completes a circuitconnecting a source of electrical energy, such as a battery 39 to asolenoid operated contactor lll. The contact 25 may be suitablyinsulated from the shaft ll and may be connected to the battery S9through a ilexible, conductive spiral spring i2 which surrounds theshaft il. Energization of the contactor lll closes a pair of contacts i3which may be the tripping contacts of any associated circuit breaker(not shown).

In order to energize the windings associated with the magnetic structurel, the windings are Rotation of the arma- The lever 3l and the stopconnected in the two arms l5 and l'l of an elec-l--f-S trical circuithaving two terminals 39 and 5l The windings il and lil, together with aresistor 53, are connected in series in the arm 45. The winding 2l,together with a resistor 55 and a capacitor El, are connected in seriesin the arm lll. The arms i? and l5 provide paths respectively for thecurrents I1 and I2. The terminals y til and 5l may be connected forenergization of the electrical circuit in accordance with the voltageacross the conductors L1 and L2 of a source of alternating electricalenergy. Instantaneous directions of flow for the currents I1 and I2 areindicated by the arrows in Fig. 1.

To provide a manual control for the direction of rotation of thearmature 9 when the windings associated therewit'n are suitablyenergized, a reversing switch 59 is provided for connecting the winding2l into the arm ill of the associated electrical circuit. If it isdesired to change the direction of the rotation of the armature 9 at anytime, the switch 59 may be actuated from the position illustrated infull lines in Fig. 1 to the position illustrated in dotted lines.

The operation of the system illustrated in Fig. 1 can be explained bestby reference to the vector representations of Figs. 2 and 3. Let it beassumed first that the electrical device of Fig. 1 is an overfrequencyrelay which is intended to close its contacts 25 and Zi@ when thefrequency of the alternating voltage E applied thereto exceeds apredetermined value. The voltage E and the currents I1 and I2 which flowthrough the arms lll and i5 in response to the voltage E are illustratedin Fig. 2. When the frequency of the voltage E is at its normal value,which is below the aforesaid predetermined value at which the relay isintended to trip, the impedances of the arms i5 and il may be designedto produce lagging currents similar to those represented in Fig. 2. Forexample, the current Il may lag the voltage E by an angle a, whereas thecurrent I2 lags the voltage E by an angle 0. Inasmuch as the currents I1and I2 are displaced from each other by the angle (6-00 a shiftingmagnetic field is produced in the air gap of the relay and a torque isapplied to the armature 9. For the conditions thus far assumed, thereversing switch 59 is so connected that the movable contact 25 is urgedby the aforesaid torque against the stop 2.

As the frequency of the voltage E increases, the reactance of thecapacitor 5l decreases. The reactance of the winding 2l increases andthe current I1 becomes more lagging with respect to the voltage. Thedirection of movement of the vector I1 in Fig. 2 as the frequencyincreases is represented by an arrow 5l. The vector I2 will also tend tolag slightly, but its movement is negligible with respect to I1, andhence may be assumed fixed in position. By inspection of Fig. 2, it willbe observed that as the vector I1 moves in the direction of the arrowiii in response to an increase in the frequency of the voltage E, itreaches a position wherein the currents I1 and Iz are in phase. This isassumed to occur when the frequency of the voltage E is at apredetermined value above which the movable contact 25 is to engage thecontact 25 of the relay. When the currents I1 and I2 are in phase, notorque is applied to the armature 9. However, if the frequency of thevoltage E continues to increase above .the aforesaid predeterminedvalue, the

value of the angle a exceeds that of the angle 0 moved from a positionwherein it leads the curf rent I2 to a position wherein it lags thecurrent I2, the direction of the torque applied to the armature 9reverses and the movable contact 25 is urged from the stop 2l intoengagement with the fixed contact 29. The time required for the movablecontact to engage the fixed contact depends on the angular distanceabout the shaft il between the fixed contact 2t and the stop 21 againstwhich the movable contact normally rests, the strength of the permanentmagnet 23 and the value of the torque applied by the magnetic structureI and associated windings to thearmature: 9'. For. any setting ofthestop 2'! relative to'. the fixed` contact 29, theV relay hasarrinverse ,time'delay with respect to the excess in frequency above thepredetermined value at which the relay is tooperate. In the case of theoverfrequency relay, the: greater the .diiference between the actual,vfrequency of the voltage E andthe predetermined frequency above whichthe A:relay is to operate, the'faster the relay closes its contacts.

From the foregoing discussion; it'will be appreciated that aslong as.theV current I1 lies within thegangulanrangeimarked open in Fig. 2, themovablel contact25isurged against its stop 21. Whenzthe current I1 lieswithin the. angular range marked trip Fig. 2; themovable contact 25isurged toward the fixed 'contact 29.

Operation` of therelay `occurs ,when the current I1 is ladjacent to thecurrentIz. As long as the values Cif-inductance; capacitance andresistance of the twoV arms 45v and til-are independentof voltage, theoperating Pointof the relay also is substantially independent of voltagesince it only depends on the phase angle between currents, and not ontheir magnitudes. Because the magnetic structure l has a magneticpermeability which may vary in accordance with the density of magneticiiux therein, the inductances of the windings may change somewhat inresponse to changes in applied voltage, However, such changes may beminimized by operating the iron well below saturation, and any smallchanges which'may occur tend to swing both currents I1 and Iz in thesamel direction with respect to the voltage E (Fig. 2) and c-onsequentlydo not change appreciably the operating point of the relay.` Forexample, in a relay actually constructed, it was found that a change involt age resulted in a change in the frequency at which'the relayoperated of only 1% of the frequency range. That is, a (S0-70 cycles persecond relay indicated an erro-r of only .01 10=.1 cycle persecond. Thissmall voltage error may be substantially eliminated in a manner pointedout-below', butin most applications an errorV of this magnitude is 'notobjectionable.

Let it be assumed next that the relay is to close its' contactsl whenthe frequency drop-s below a predetermined value. When the frequency ofthe voltage is below the predetermined Value, the vec tor relationshipsmay be siniilar'to those illustratedin Fig` 3; It'will be noted that thecur' rent I2 now leads the current I1. IThe reversing switch 53 is sopositioned that a torque applied to the armature 9 when the vectors ofthe currents I1 and Izoceupy the positions illustrated in Fig; 3 urgesthe movable contact against the stop 21." As the frequency drops, thereactance of the capacitor 'l increases and the current I1 becomes lesslagging. At the predeterminedvalue of frequency above which the relay isto operate; the current I1 is substantially in phase with the cur-y rentI2; The direction of'rotation of 'the current I1 as the frequency dropsis represented in Fig. 3 by an arrow 63.

If the frequency dro-ps below'the aforesaid predetermined value, thecurrent I1 leads the current I2 and the direction of the torque applied'to the armature 9 reverses to urge the movable contact 25 intoengagement with thel contact 29. The relay operates with-a time delaysimilal` to that discussed for overfrequency operation.

The effect of variations in ambient temperature now maybe considered. Inresponse to a change,

in temperature, theginductances of the windings:

Il; I Sand 2| may change slightly. However, such changes tend to` rotatethe vectors I1 and I2 of Figs,- 2 and 3V in'the same direction withrespect to the voltageE. Consequently, such changes in inductance are toa substantial extent self-compensating. Resistors having substantially azero temperature coefficient ofresistance and capacitors havingsubstantially a Zero temperature coefiicient of capacitance areavailable. Consequently, by selecting suitable resistors and capacitors,the relay illustrated in Fig. 1 may be made substantially free of errorsintroduced by ambient temperature.

In an electrical relay embodying the invention which was constructed'and tested, it was'found that a capacitor having a Zero temperaturecoei'cient of capacitance in association with suitably selectedresistors provided a frequency relay wherein the tripping frequencyVaried only slightly with variations in relay temperature. Even betterperformance wasY obtained by employing a capacitor having a temperaturevariation of capacitance of -.04% per degree oentigrade, tocompensatefor the variation in resistance of the copper, used to windcoils Il, i9, 2|. Capacitors having'a negative temperature variation ofthis magnitude are readily available -on the market. In the relayemploying a capacitor having a nega tive temperature variation ofcapacitance and adjusted to trip at a frequency of 55 cycles per second,it was found that the tripping frequency varied less than plusV or minus116 of a cycle per second over a temperature range of -20 to 65 C.

In order to vary the frequency at which the relay trips, one of theresistors 53 or 55 may be adjustable. In Fig. l, the resistor 53 isindicated as being adjustable for this purpose. Referring to Fig. 2, itwill be observed that theeffect of an increasein the resistance value ofthe resistor 53 is to decreasefthe valueof the angle 6. This decreaseslthe Value-of the frequency at which the currents I1 and I2 are in'phase.Consequently, by adjustment of the resistor 53. the tripping frequencyof the relay may be adjusted over a suitable range, such-as l@ cyclesper second. For example, a relay was constructed to operate at anyfrequency within arange between 50 and 60 cycles per second,`Adjustment'of the relay within this range has little elf-ect on othercharacteristics of therelay. Errors due to voltage and temperatureYvariations were negligible at all points within'therange of adjustmentof the instrument.

It has beenfound that the values of inductance, capacitance andresistance present in the arms l5 and 4'! mayvary over a wide range solong as they-are coordinated to provide a desired relay response.However, certain principles may be laid dcwn-foroptimum performance. Theimpedancesv ofthe arms 15J-and 'lmav be represented by the followingsymbols:`

L1 is the inductance present in the arm 4l C1 is the capacitance presentin the arm il f is the frequency at which the currents I1 and I2 are inphase Ri is the resistance present in the arm 4l.

For optimum performance, it isdesirable that be small. Thev value of L1should belarge and 7 the value of Ci should be small. This gives a largevariation in phase angle for small variations in frequency. Furthermore,for optimum performance, the value of resistance should be selected inaccordance with the following expression:

As previously pointed out, the errors introduced by variations inapplied voltage are extremely small. However, if it is desired to renderthese errors still more negligible, a voltage bias winding may beprovided for applying a compensating torque to the armature 9 which hasa magnitude dependent on the magnitude of the applied voltage. Thedirection of the compensating torque depends on the nature of thecorrection required.

If the tripping frequency decreases as the applied voltage decreases foran underfrequency relay or if the tripping frequency increases as theapplied voltage decreases in the case of an overfrequency relay, thenthe compensating torque applied to the armature 9 by the voltage biaswinding should oppose the relay operating torque.

If the tripping frequency increases as the applied voltage decreases inan underfrequency relay or if the tripping frequency decreases as theapplied voltage decreases in the case of an overfreduency relay, thenthe compensating torque applied to the armature 9 should aid theoperating torque of the relay. By this expedient, the small voltageerrors otherwise present may be substantially eliminated.

To illustrate a suitable structure for compengating for voltage errors,reference may be made to Fig, 4. In Fig. 4 a portion of the frequencyrelay of Fig. 1 is illustrated. However, the pole face of the pole piece1 is shaded by a bias winding 65 which is adjustable across the face ofthe pole piece. This winding may be in the form of a single shortcircuited loop or plate of electroconductive material. Depending on itsadjustment with respect to the pole face, the winding E55 applies acompensating torque to the armature .'i which aids or opposes the relayoperating torque. Since the magnetic ilux passing through the shadingwinding t depends on the current passing through the winding 2l, andsince such current varies as a function of the applied voltage, itfollows that the winding 65 produces a compensatingr torque which isdependent on the magnitude of the applied Voltage. Such shading windingsare commonly employed for friction compensation in watthour meters andthe construction and operation thereof are well known.

Effective compensation for voltage errors is provided by the arrangementshown in Fig. 5. The magnetic structure i, windings l1. I9 and 2l andthe connections illustrated in Fig. 1 also are employed in thearrangement of Fig. 5. eX- cept that for simplicity the switch 59 isomitted. In addition a winding B5 is employed which is energized throughan adjustable resistor 53 and a reversing switch 'i0 from the terminals49 and 5l. The magnetic ux produced by the winding 66 is substantiallyproportional to the voltage applied to the terminals 49, 5l. Dependingon the position of the reversing switch 'l0 this magnetic flux coactswith the magnetic fluxes produced by the remaining windings to produce acompensating torque which aids or opposes the torque developed by thewindings Il, i9`and 2i alone. By adjustment of the resistor 68, themagnitude of the compensating torque may be adjusted to compensatesubstantially for voltage changes.

Although the invention has been described with reference to certainspecific embodiments thereof, numerous modifications thereof arepossible and, therefore, the invention is to be restricted only by theappended claims as interpreted in view of the prior art.

I claim as my invention:

1. In an electrical relay device which is responsive to a predeterminedvariable characteristic of a variable quantity, means eifective whenenergized by an alternating quantity for producing a pair of alternatingelectrical components having a phase relationship dependent on apredetermined variable characteristic of a quantity, said electricalcomponents being in phase for a predetermined value of the quantity, andtranslating means responsive to the passage of said phase relationshipbetween said alternating electrical components through said in-phasecondition, whereby said translating means is responsive to thepredetermined variable characteristic.

2. In an electrical relay device which is responsive to a predeterminedvariable characteristic of a variable quantity, a parallel circuithaving two arms connected in parallel for energization from a commonsource of alternating energy, said arms having an impedance relationshipresponsive to a predetermined variable quantity for producing a phaserelationship between the two currents owing in said arms which varies asa function of said variable quantity, said electrical currents being inphase for a predetermined value of the variable quantity, meansadjustable for varying the phase relationship between the two currentspassing through said arms, and translating means responsive to passageof said phase relationship through said irl-phase condition.

3. In an electrical relay device, a directional element comprising afirst winding, a second winding and means directionally responsive tothe direction of deviation of the phase relationship between alternatingcurrents traversing said windings from an in-phase relationship, meansconnecting said windings in parallel for energization from a commonsource of alternating energy, means responsive to a predeterminedvariable quantity for varying the phase relationship between alternatingcurrents traversing said windings through an in-phase condition, wherebysaid directional element is responsive to said variable quantity, andmeans for adjusting the time of response of said relay device to adeviation of said alternating currents from an inphase relationship.

4. In an electrical relay device, a directional element comprising a rstwinding, a second winding and means directionally responsive to thedirection of deviation of the phase relationship of one alternatingcurrent relative to another alternating current traversing said windingsfrom an in-phase relationship, means connecting said windingsrespectively in two parallel arms of an electrical circuit forenergization from a common source of alternating energy, said armshaving impedances proportioned to produce iii-phase currents when saidarms are energized from a source of electrical energy alternating at apredetermined frequency, said impedances being responsive to deviationof the source from said predetermined frequency for producing acorresponding deviation of the phase relationship of said currents fromsaid in-phase relationship, whereby said directional element isresponsive to the direction'of deviation of said source from said pre- Adetermined frequency. l

5. In an electrical relay device, a'directional element comprising a rstwinding, ya second winding and means directionally responsive to thedeviation of the phase relationship between i alternating currentstraversing said iwindings from a predetermined relationship,means'connecting said windings respectively in two parallel arms of anelectrical circuit for energization from a common source of alternatingenergy, said f arms having impedances proportioned to produce 6. .In anyelectrical relay device responsive to the frequency of an alternatingquantity, a directional element, an armature member, means mounting saidarmature member for rotation, a first winding, a second winding, saidwindings being effective when energized respectively by a firstalternating current and by a second alternating current for producing amagnetic field acting to urge said armature member in a directiondependent on the direction of deviation of said rst alternating currentfrom an in-phase relationship relative to said second alternatingcurrent, and means connecting said first and second windingsrespectively in first and second parallel arms of an electrical circuitfor energization from a common source of alternating voltage, said armshaving impedances proportioned to establish a phase relationship betweencurrents passing through said arms which varies as a function of thefrequency of the alternating voltage applied to the electrical circuitover a range which includes said in-phase relationship, electricalcontact means responsive to actuation oi said armature member, wherebysaid contact means is controlled in accordance with the frequency ofsaid alternating voltage, and time delay control means for adjusting theamount of rotation of said armature member required to operate saidcontact means.

7. In an electrical relay device responsive to the frequency of analternating quantity, a directional element, an armature member, meansmounting said armature member for rotation, a first winding, a secondwinding, said windings being eifective when energized respectively by afirst alternating current and by a second alternating current forproducing a magnetic eld acting to urge said armature member in adirection dependent on the direction of deviation of said firstalternating current from an in-pliase relationship relative to saidsecond alternating current, and means connecting said first and secondwindings respectively in first and second parallel arms of an electricalcircuit for energization from a common source of alternating voltage,said arms having impedances proportioned to l1l) establish a phaserelationship between currents passing through saidarms which varies as afuncftion of the frequency of theA alternating Yvoltage 'applied to theelectrical circuit overa range which includes/said in-phaserelationship, means for adjusting the impedances of said arms to changethe frequency of the' alternating voltage 'at which 'said predeterminedphase relationship is established, and-electrical contactmeansresponsive tof actuation of said armature memberfwhereby sai/icontact means is control-led in accordance .with the frequency of'saidalternating voltage, and time-delay-controlmeans foradjusting the amountof rotation of said armature member required to operate said contactmeans,

8. In an'electrical relay `device which is responsive to Va frequency,means eliective when .energized by an valternating voltage quantity forproducing a pair of-alternating electrical com- .ponents having a phaserelationship dependent on frequency, translating means responsive to thephase relationship between said alternating electrical components,whereby said translating means in responsive to frequency, saidtranslating means being subject to error resulting to magnitudevariations of said voltage quantity, and means responsive to variationsin the voltageof said alternating -voltage quantity for applyingto saidtranslating means anauxiliary enfergization proportionedtovneutralize'the effects of such voltage variations on the response ofsaid translating means.

9. In an electrical relay device which is responsive to a predeterminedvariable characteristic of a variable quantity over a substantial rangeof temperature, a parallel circuit having two arms connected in parallelfor energization from a common source of alternating energy, said armshaving an impedance relationship substantially responsive to apredetermined variable quantity for producing a phase relationshipbetween the two currents iiowing in said arms which varies substantiallyas a function of said variable quantity, and translating meansresponsive to said phase relationship, whereby said translating means issubstantially responsive to said variable quantity, the impedance of oneof said arms having a substantial temperature coeflicient proportionedto neutralize the effects of temperature variations on the response ofsaid translating means to said variable quantity.

10. In an electrical relay device, a directional element comprising arst winding, a second winding and means responsive to the phaserelationship between alternating currents traversing said windings,means connecting said windings in parallel for energization from acommon source of alternating energy, means responsive to the frequencyof an applied alternating voltage for varying the phase relationshipbetween alternating currents traversing said windings, said directionalelement being responsive in some degree to variations in the magnitudeof said alternating voltage, and means responsive to the magnitude ofsaid alternating voltage for applying to the directional element anauxiliary energization proportioned to neutralize the eiects ofvariations of the magnitude of said alternating voltage on thedirectional element, whereby said directional element is responsive tothe frequency of an applied alternating voltage.

l1. In an electrical relay device, a directional element comprising afirst winding, a second winding and means directionally responsive tothe deviation of the phase relationship between '1l alternating currentstraversing said windings from a predetermined relationship, meansconnecting said windings respectively in two parallel arms of anelectrical circuit for energization from a common source of alternatingenergy, the impedances of said arms determining the phase relationshipbetween alternating currents traversing said arms in response to theapplication of an alternating voltage applied across said electricalcircuit, at least one of said impedances being reactive for varying thephase relationship between currents traversing said arms as a functionof the frequency of the applied alternating voltage, said electricaldevice being responsive in some degree to the temperature of the portionof said electrical circuit other than said one of said impedances, saidone of said impedances having a substantial temperature coeiicient ofimpedance proportioned to compensate said electrical device foroperation over a substantial temperature range, whereby said directionalelement is responsive to frequency of the applied alternating voltageover a substantial temperature range.

12. In an electrical relay device, a directional element comprising arst winding, a second winding and means directionally responsive to thedeviation of the phase relationship between alternating currentstraversing said windings from a predetermined relationship, meansconnecting said windings respectively in two parallel arms o! anelectrical circuit for energiz'ati from a common source of alternatingenergy, the impedances of said arms determining the phase relationshipbetween alternating currents traversing said arms in response to theapplication of an alternating voltage applied across said electricalcircuit, at least one of said impedances being reactive for varying thephase relationship between currents traversing said arms as a functionof the frequency of the applied alternating voltage, said electricaldevice being responsive in some degree to changes in magnitude of theapplied alternating voltage and to the temperature of the portion ofsaid electrical circuit other than said one of said impedances, said oneof said impedances having a substantial temperature coefficient ofimpedance proportioned to compensate said electrical device foroperation over a substantial temperature range, and means responsive tothe magnitude of the applied alternating voltage for applying to saiddirectional element an auxiliary energization proportioned to neutralizethe effects of variations of the magnitude of said alternating voltageon the electrical device, whereby said directional element is responsiveto frequency of the applied alternating voltage over a substantialtemperature range, and over a substantial range of voltage.

HERBERT J. CARLIN.

